diff --git a/lib/AST/MicrosoftMangle.cpp b/lib/AST/MicrosoftMangle.cpp
index ba9856a..6250f61 100644
--- a/lib/AST/MicrosoftMangle.cpp
+++ b/lib/AST/MicrosoftMangle.cpp
@@ -763,12 +763,16 @@
     Out << 'X';
   } else {
     if (D) {
-      // If we got a decl, use the "types-as-written" to make sure arrays
-      // get mangled right.
+      // If we got a decl, use the type-as-written to make sure arrays
+      // get mangled right.  Note that we can't rely on the TSI
+      // existing if (for example) the parameter was synthesized.
       for (FunctionDecl::param_const_iterator Parm = D->param_begin(),
-           ParmEnd = D->param_end();
-           Parm != ParmEnd; ++Parm)
-        mangleType((*Parm)->getTypeSourceInfo()->getType());
+             ParmEnd = D->param_end(); Parm != ParmEnd; ++Parm) {
+        if (TypeSourceInfo *typeAsWritten = (*Parm)->getTypeSourceInfo())
+          mangleType(typeAsWritten->getType());
+        else
+          mangleType((*Parm)->getType());
+      }
     } else {
       for (FunctionProtoType::arg_type_iterator Arg = Proto->arg_type_begin(),
            ArgEnd = Proto->arg_type_end();
diff --git a/test/CodeGenCXX/mangle-ms.cpp b/test/CodeGenCXX/mangle-ms.cpp
index fe5fde1..ceaa669 100644
--- a/test/CodeGenCXX/mangle-ms.cpp
+++ b/test/CodeGenCXX/mangle-ms.cpp
@@ -103,3 +103,17 @@
 void zeta(int (^)(int, int)) {}
 // CHECK: @"\01?zeta@@YAXP_EAHHH@Z@Z"
 
+void operator_new_delete() {
+  char *ptr = new char;
+// CHECK: @"\01??2@YAPAXI@Z"
+
+  delete ptr;
+// CHECK: @"\01??3@YAXPAX@Z"
+
+  char *array = new char[42];
+// CHECK: @"\01??_U@YAPAXI@Z"
+
+  // FIXME: enable once PR12333 is fixed
+  // delete [] array;
+// Should be: @"\01??_V@YAXPAX@Z"
+}